An inkjet recording device provided with a recording head having a plurality of nozzle rows corresponding to a plurality of ink colors is well known in the art. The device records an image represented in image data by reciprocating the recording head while ejecting ink from the nozzle rows based on the image data.
In order to improve the speed at which images are recorded, this type of inkjet recording device may perform bi-directional recording in which an image is recording by ejecting ink from the recording head in both a forward direction and a reverse direction of the reciprocal motion. Here, the different sequences in which the colors of ink are superposed between the forward scan and reverse scan can lead to irregularities in color (referred to as “color banding”). However, since the degree in which such color banding is noticeable depends on the image, a method has been proposed for recording areas of an image in which color banding would be more noticeable by single-direction recording.
Specifically, for each region of an image that is recorded in either one forward scan or one reverse scan of the recording head (hereinafter referred to as a “scanning region”), the conventional recording device employing the above method determines whether the image in any portion of this scanning region is susceptible to noticeable color banding. The device performs bi-directional recording when determining that the scanning region has no areas in which color banding is noticeable, and performs single-direction recording when determining that the scanning region has areas in which color banding may be noticeable. More specifically, the recording device scans the image data within two detection areas (windows) of the scanning region to detect an image with a high quantity of ink (a high recording duty) and calculates the ink quantity within the detection areas at each scanning position of the window. Based on these calculations, the recording device performs bi-directional recording when there exists no detection areas having an ink quantity greater than a reference value and performs single-direction recording when there exists even one such detection area.